FRIDAY, April 3 (HealthDay News) -- Exposure to higher levels of environmental lead earlier in the life span may be taking a toll on the brains of older American women, a new study finds.

The Harvard study shows that women aged 47 to 74 who tested positive for lead in their blood (indicating a recent exposure to the metal) or bones (an indication of cumulative exposure over the life span) did somewhat worse on cognitive tests than those who did not show signs of lead exposure.

In the study, the researchers noted that regulatory changes phased out higher lead content in products such as gasoline during the 1980s, so that lead is at a relatively low level today.

So, only those women with lead biomarkers found in their tibia bone, an indication of long-ago exposure, scored poorly enough to be considered statistically significant, according to the study.

The study, which analyzed lead levels and cognitive scores in almost 600 women from the Boston area, is in the April issue of Environmental Health Perspectives.

"Findings in this study are important because of their long-range consequences on the public health of an aging generation," the journal's editor-in-chief, Hugh A. Tilson, said in a journal news release. "Impaired cognition and cognitive decline in older women are associated with heightened risks of dementia, physical disability, hospitalization and reduced quality of life in later years."